Why can X-rays see inside people's bodies?

X-rays can penetrate substances that ordinary visible light cannot penetrate. Because visible light waves are long, their energy is very small. When it touches an object, part of it is reflected, most of it is absorbed by matter, and it cannot penetrate the object. On the other hand, x-rays are not. Because of their short wave length and high energy, when they shine on matter, only a part of them are absorbed by matter, and most of them pass through the gaps between atoms, showing strong penetration ability. The ability of X-rays to penetrate matter is related to the energy of X-ray photons. The shorter the wavelength of X-ray, the greater the photon energy and the stronger the penetrating power. X-ray penetration is also related to the density of matter. Substances with high density absorb more X-rays and transmit less. Low density has less absorption and more penetration. Using the characteristics of differential absorption, soft tissues such as bones, muscles and fat with different densities can be distinguished.